Body fluid homeostasis depends on reflexes which act to modulate the rate of renal water and sodium loss and on ingestive behaviors (i.e. thirst and salt appetite) that correct deficits. Although renal mechanisms can slow fluid loss the restoration of vascular volume depends on the ingestion of water and solute (i.e. sodium). The maintenance of extracellular volume requires that the CNS receives and processes information about the status of body water and sodium. Several visceral sensory systems are known to provide this afferent input, but there is only limited understanding about how this information is handled by the CNS. The present FIRCA proposal extends and builds upon the PI's prior studies on the central processing of afferent signals involved in body fluid and cardiovascular control and will couple the neuroanatomical expertise of Dr. de Olmos in Argentina with the functional studies of Dr. Johnson in the U.S. and Dr. Vivas in Argentina. The general goal of the study is to examine the role of the extended amygdala in the control of sodium appetite and body fluid control. The investigators will use the rapid-onset model of salt appetite and then perform a functional anatomical analysis of the extended amygdala. The F0S immunohistochemical technique will be employed to assess the effects of manipulations made to affect salt appetite, blood volume, blood pressure and 5-HT activity in the lateral parabrachial nucleus on neuronal activity in the extended amygdala. Such new information will advance our knowledge of how the brain processes information related to body fluid and cardiovascular homeostasis.